Portable seat cushion



FIG. 1 is a top plan view showing my new design for a portable seat cushion, the bottom plan view being identical;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a side elevational view thereof, both sides being identical; and,

FIG. 5 is a perspective view thereof. 

The ornamental design for a portable seat cushion, as shown and described. 